Isolation and characterization of defined populations of immunologically competent cells and their products should facilitate investigations designed to elucidate the mechanism of antigen recognition at the cell surface, the nature of the receptors and the genetic control of such recognition. The intention here is to prepare cellular immunoabsorbants using a dextranase digestible insoluble support of Sephadex which will permit both depletion and recovery of populations of functionally viable lymphocytes according to their surface properties. Specific T-cells, B-cells and null cells will be studied either separately or in recombined pools both in vivo and in vitro to elucidate their role in the induction of the immune response. The technique for fractionation of lymphoid cells into functionally viable populations with specific receptors for antigen will be utilized in attempts to define the chemical nature, the mode of attachment, distribution and specificity of the receptors on both T- and B- cells. Moreover, studies of genetic control of immune responses have been outlined which use both the limited heterogeneity of antibodies and the sensitive measures of T- and B-cell responses to defined alpha, DNP- oligolysines. With use of isoelectric focusing to define antibody responses in clonal terms and the development of anti-idiotypic antibodies to these clones we intend: 1) to determine the cellular site for immune response gene control; 2) to ascertain the V-gene pool size to defined antigens; 3) to segregate those genes governing antibody specificity from those regulating the magnitude of the immune response; and 4) to investigate the factors controlling the persistence and heterogeneity of a clonal response to defined DNP-oligolysines.